Allergic versus Contagious Conjunctivitis: Do you know the difference?

Tired of dealing with red, itchy eyes? The kind that look suspiciously ‘pink’ and warrant that dreaded ‘quarantine’? Is it conjunctivitis? Before you panic about screen time (yes, you should reduce that anyway), there are two main suspects: Allergic conjunctivitis and contagious conjunctivitis. While both cause redness and discomfort, knowing the difference is crucial for seeking the right treatment and preventing the spread of infection.

Eye discomfort, characterised by redness, itching, or excessive tearing, is a common concern for various reasons. Two prevalent reasons are contagious conjunctivitis, caused by viral bacterial infections, and allergic conjunctivitis, triggered by exposure to allergens. The good news? The latter isn’t as contagious as you think.

What is conjunctivitis?

Conjunctivitis or pink eye is an inflammation of the eye’s thin, protective membrane called the conjunctiva. It can result from infections, allergies, or irritants, causing redness, itching, tearing, and discharge. 

Conjunctivitis didn’t pop out of the blue in modern times. Our obsession with kohl isn’t just for the sake of vanity. Kohl or kajal is traditionally believed to be ‘medicinal’ in nature. It was originally made by grinding stibnite (a sulfide mineral) or galena (lead sulfide). The lead properties might have actually staved off an eye infection or two. However, there is, and was always, the more dangerous risk of lead poisoning. But seeing that doctors were scarce (read non-existent ) in ancient times, kajal gained the reputation of being more than just protection against the evil eye.   

Some experts even believe that in ancient Egypt, when the Nile flooded, Egyptians suffered from infections caused by particles that entered the eye. Their lead-based makeup acted as a barrier, killing bacteria before they spread.

Types of conjunctivitis: Viral, bacterial, allergic & more

Conjunctivitis can be caused by infections, allergies, irritants, or underlying conditions. Understanding the different types can help one recognise symptoms and seek appropriate treatment.

Viral conjunctivitis

This is the most common and highly contagious form. It's usually caused by the same viruses responsible for the common cold.

Symptoms include:

• Watery discharge

• Redness in one or both eyes

• Gritty sensation

• Often accompanied by cold or flu symptoms

Bacterial conjunctivitis

This form is caused by bacteria such as Staphylococcus aureus, Streptococcus pneumoniae, or Haemophilus influenzae. It is also contagious and more common in children.

Symptoms include:

• Thick, yellow, or green discharge

• Crusting of the eyelids, especially after sleep

• Redness and irritation

• Usually affects one eye first, then possibly the other

Allergic conjunctivitis

This type is triggered by allergens such as pollen, dust mites, pet dander, or mould. It is not contagious.

Symptoms include:

• Itchy, watery eyes

• Redness and swelling

• Often occurs with hay fever or other allergic symptoms

• Usually affects both eyes

Giant papillary conjunctivitis (GPC)

Usually associated with long-term contact lens use or an allergic reaction to lens solutions.

Symptoms include:

• Itching and mucus discharge

• Blurred vision

• Bumps on the underside of the eyelid

• Lens intolerance or discomfort

How do doctors diagnose conjunctivitis?

Doctors diagnose conjunctivitis by examining the patient’s symptoms, asking about recent exposures, and assessing the appearance of the eyes. They take into account factors such as the type of discharge, presence of irritation or itching, whether one or both eyes are affected, and any accompanying health issues. A thorough medical history helps determine whether the conjunctivitis is likely to be caused by an infection, allergies, or irritants. In some cases, if the cause is unclear or symptoms are severe or prolonged, further assessment may be needed to guide appropriate treatment.

What is the major difference between contagious and allergic conjunctivitis?

Here’s how contagious and allergic conjunctivitis differ:

Contagious conjunctivitis

It’s caused by viruses or bacteria that can spread via contact with infected eyes, hands, or contaminated objects like handkerchiefs, towels, or shared eye makeup. Symptoms typically appear suddenly and may include itchy or burning eyes, redness, excessive tearing, pus discharge, and crusting around the eyelashes. 

Allergic conjunctivitis

Triggered by an allergic reaction to pollen, dust mites, pet dander, or other allergens and usually affects both eyes. Is allergic conjunctivitis or allergic pink eye contagious? No, but symptoms often occur seasonally or when exposed to the allergen. They may include itchy, watery eyes, redness, and swollen eyelids.

Doc talk

To understand more about the topic, we spoke to ophthalmologist Dr Mandeep Singh Basu, from Basu Eye Hospital, New Delhi.

Q: How long do symptoms last, and when should people seek immediate medical attention?

Dr Basu: It depends on the cause. Conjunctivitis symptoms last for different periods. As long as the allergen exposure occurs, allergic conjunctivitis may recur, although bacterial or viral infections usually clear up in one to two weeks with appropriate care. It is essential to seek medical assistance if symptoms worsen or continue after this period. If you experience severe eye pain, changes in your vision, extreme redness, or light sensitivity, you should get medical attention immediately. These symptoms could indicate a more severe issue or complications, suggesting immediate care to avoid potential blindness. Regular follow-ups can ensure appropriate management and healing.

Q: Are there any lifestyle changes I can adopt to reduce the likelihood of recurrence?

Dr Basu: Work closely with your healthcare expert to identify specific allergens triggering your reactions. Avoid touching your eyes too often. Be cautious of the quality of eye makeup used and avoid sharing eye products. Allergen-proof your home with covers on pillows and mattresses; keep your living space clean; and consider using air purifiers. When outside, think about wearing shades to protect your eyes from airborne irritants. Limit exposure to pet dander if it triggers you, or make sure your pet is well-groomed. Adherence to prescribed allergy medications, regular check-ups with healthcare providers, and staying informed about allergy management strategies contribute to a comprehensive approach to reducing the recurrence of allergic reactions.